Pendulum compensated surveying instrument



y 1952 R. T. CLOUD 2,598,355

PENDULUM COMPENSATED SURVEYING INSTRUMENT Filed Sept. 13, 1946 5 Sheets-Sheet 1 May 27, 1952 R. T. CLOUD ,598,

PENDULUM COMPENSATED SURVEYING INSTRUMENT Filed Sept. 15, 1946 5 Sheets-Sheet 2 Fig. 2

IN VEN TOR.

R. 7. Cloud M w; BYX if g y 1952 R. T. CLOUD 2,598,355

PENDULUM COMPENSATED SURVEYING INSTRUMENT Filed Sept. 15, 1946 5 Sheets-Sheet 5 A TTORNEYS May 27, 1952 v R. T. CLOUD 2,598,355

PENDULUM COMPENSATED SURVEYING INSTRUMENT Filed Sept. 13, 1946 5 Sheets-Sheet 4 Fig 5 INVENTOR. RI Cloud BY W M AT TOR/VEYS May 27, 1952 R. 1'. CLOUD 2,598,355

PENDULUM COMPENSATED SURVEYING INSTRUMENT Filed Sept. 13, 1946 5 Sheets-Sheet 5 IN V EN TOR.

M Fig W 45% ATTORNE Y5,

Patented May 27, 1 952 UlTED STATES PATENT OFFICE PENDIJLUM .COM PENSATED SURVEYING INS-TRUMEN T Raymond "I. Cloud, Houston, Tex., assignorto North American Geophysical 00., Houston, .Tex a corporation of Texas ApplicationSeptember 13, 1946, SerialNo. 696,789

-31 E=kjg sin qbfi's Where: I

E=difierence in elevation lc=constant of apparatus =angle of terrain I s=distance traversed 'I-leretofore apparatus for accomplishing this have not-been entirely-satisfactory. No ,difliculty has beenencountered in themeasurementof distance. However, the measurement of the instantaneous angle of the ;vehicle with the accuracy necessary to provide adevice having an accuracy of plus or minus six inches (8) to the mile has presented difficulties not heretofore-satisfactorily solved. To 'providesatisfactory mechanism of the type employing a pendulum to measure the angle the measurementof the angle'must be with an accuracy in theneighborhoodol onethird of a degree or about twenty 2(3) seconds of are. I I

Some of the features which contribute to the difficulties involved 'the'measure'meiit oi the angle when the apparatus is mounted on the floor of an ordinary spring suspended :car body are enumerated below:

1. The pendulum may deviate from the per pendicular due to the acceleration-or deceleration of the cars motion in .a 'forwardidire'ction.

2. The solid friction of the :pendulum s .bearings may cause the pendulum to deviate from a true perpendicular position.

3. The spring suspension :of the car body changes and introduces an error. into the apparatus as the angle of :the'body1ielative to the horizontal does not represent true angle encountered by the 'automobiletires.

(e) Unequal distribution of the vehicle load due to shift of driversposition, extra passengers,

or other articles placed on -or-removed from the car, as well as-the difference in the weight of gasoline carriedi-nlthe car-tank. (c) The effect of wind upon the car body.

it is the general object of the present invention to eliminate the difficulties heretofore encountered and to this end there is provided a novel apparatus which will be explained 'in the following description and includes difierent em- 'bodiments'suitable for carrying the invention into effect.

"More specifically, an'ohject 10f the invention is to provide asuitab'le pendulum in the form'ofa disc having-unsymmetrical cut-away portions.

Another object is to provide a mounting for the pendulum such that the pendulum is free to "hang true to the perpendicular as the vehicle angle of inclination. varies.

A further object is to providemeans for'ro- 'tatin'g the support from which the pendulum is suspended, about an'axis alignedwith 'the pendulum suspension, the rotation being relative to the vehicle and insubstantial unison with the pendulum. I

Still another object is to, provide a pendulum support which .is rotatable in unison with the pendulum wherein the support carries ,a means for imposing a'magnetic flux about thependulum rim to retard vibration and oscillation of the pendulum.

Still afurtherobject is to provide inan apparatus of the character described, a means 'for applying forces tothe pendulum which are equal and opposite indirection to those imparted to the pendulum by -variations in vehicle acceleraion. a

Yet.anotherolcueot is -to-provide apparatus of the character described which-may have aspring mounting on a vehicle and means for compensating for the angle between the unsprung vehicle chassis and .the'cushion mounting.

Yet a further object is to provide in an :appa- :ratus of the character described, 'means .for .zrendering the apparatus inefiective when theangle encountered by the vehicle or the speed of the vehicle exceeds predetermined limits together with means for notifying the operator when this occurs.

Even anotherobject is to provide a large scale saw-tooth type recording of the elevation variations along thepathof thevehicle. I I I Other and further objects will appear from the following description.

In the accompanying drawings, which form a part of the instant specification and are to be read in conjunction therewith and where like reference numerals are used to indicate like parts in the various views,

Fig. 1 is a perspective schematic view illustrating the principle of an embodiment of the invention;

Fig. 2 is a plan view, with parts removed for clarity, of the preferred embodiment of this invention;

Fig. 3 is a view taken along the line 3-3 in Fig. 2 in the direction of the arrows;

Fig. 4 is a view taken along the line 4-4 in Fig. 2 in the direction of the arrows;

Fig. 5 is a view taken along the line 5-5 in Fig. 2 in the direction of the arrows;

Fig. 6 is a view taken along the line 8-6 in Fig. 5 in the direction of the arrows;

Fig. 7 is a view taken along the line '.'--l in Fig. 5 in the direction of the arrows;

Fig. 8 is a view taken along the line 8 in Fig. 3 in the direction of the arrows, and illustrating the magnetic clutch assembly;

Fig. 9 is a side elevational view of a recording assembly constituting a part of this invention;

Fig. 10 is an end view of the assembly shown in Fig. 9;

Fig. 11 is a fragmentary plan view illustrating the form of the chart drawn by the assembly shown in Figs. 9 and 10; and

Fig. 12 is a schematic view of a modified type of acceleration compensator impeller element.

It is believed that the apparatus of this invention may be more readily understood by first referring to the schematic drawing of Fig. 1, which illustrates the principle of the invention, and considering the component parts thereof. The apparatus may be considered as comprised of the following component parts:

The pendulum and the follow-up system from which the pendulum is suspended with the means for rotating the follow-up support arm in unison with the pendulum;

An acceleration compensator or the means for imposing upon the pendulum a force equal and opposite to that imparted to the pendulum by acceleration and deceleration of the vehicle;

An angle correction device including a parallel arm straight line mechanism whereby a difieren- I tial angle between the base of the apparatus and a bar or unsprung vehicle chassis is added or subtracted, as the case may be, so the direct angle is introduced into the sine converter.

The sine converter which is connected to the drive for the follow-up system and the unsprung vehicle chassis and which is efiective to convert the true angle into the sine thereof;

The integration mechanism or means for integrating the sine of the true angle times the differentia1 of the distance traveled between selected limits;

The limit switches which control operation of the device de-energizing the device and energizing an alarm when the angle encountered by the vehicle or the speed of the vehicle exceeds predetermined limits; and

The charting mechanism for plotting the elevation variance against distance traveled as detailed in Figs. 9, l0 and 11 of the drawings.

Referring to the drawings, the invention will be discussed in detail. In the discussion each of the major component parts of the apparatus will for convenience be considered separately.

4. Pendulum and follow-up system In the apparatus of this invention the pendulum [5 may be considered as the real heart thereof and remains in a vertical position where by the center of mass remains directly below the center of suspension at all times, thus, the vertical acceleration imposed by the car motions produce no turning moment about the axis of the pendulum.

This may be accomplished by mounting the pendulum upon a follow-up arm or support which is rotatably mounted. The axis of rotation of the follow-up arm and the axis of oscillation of the pendulum must be in alignment. This mounting is essential to proper functioning of the device. By this expedient the torsion wires or the ball bearings which suspend the pendulum serve merely to measure the instantaneous deviation of the pendulum from the follow-up arm. On the other hand if the pendulum were suspended from the main frame of the device this deviation would be much greater, as it would be the angle of deviation between the pendulum and the vehicle. Inasmuch as the follow-up arm moves in substantial unison with the pendulum the torsion of the wire or the friction of the ball bearings,. as the case may be, is substantially eliminated. When the ball bearings are used the proper relation of the inner and outer races to each other is assured whereby the true normal or vertical position of the pendulum may be maintained. In both cases this is important. Otherwise, the residual torsion in the wire would cause a deviation of the pendulum from the vertical. In the case of ball bearings even the most perfect precision ball bearings available have slight irregularities which in operation results in an angular deviation of the pendulum from the vertical position.

The center of suspension of pendulum i5 is along the line indicated by the arrows and is aligned with the axis of rotation of follow-up arm or support 16. The pendulum may be suspended by a torsion wire, ends of which are anchored to support IE or may be carried by ball bearings supported by arm l6. Rotation of arm [6 with the pendulum is accomplished by the photo-electric cell assembly including cells I! and I8 mounted in carrier 19. Light from lamp 20, as indicated by the dotted lines, passes through the lower cut-away portion of pendulum I5, is reflected by mirrors 2!, also mounted on the support l6, through the upper cut-away portion to the photo-cells. In the position shown in Fig. 1 approximately half of each cell is exposed to the reflected light imparting an equal electric potential to the cells. Obviously when pendulum 15 rotates relative to the followup system an unequal distribution of the light results in a potential differential which is accentuated by amplifier 22. The accentuated potential energizes a servomotor shown in the form of the solenoid 23.

The solenoid or servomotor controls the drive mechanism for rotating the follow-up arm to the position of equilibrium with respect to the photo cells. The drive mechanism includes the constant speed motor 24. The motor arbor carries a pinion gear 26 which meshes with gear 27 keyed to shaft 28. Shaft 28 rotates disc 29 at a constant speed by virtue of the spiral gear assembly 30. Mounted above disc 29 is a roller 3! keyed to shaft 32. Ball cage 33 positioned between disc 29 and roller 3i carries two balls in frictional engagement with one another and the l werball fr ctionally en ages disc 19 .and t e ono ball frictional-1y en ages roller :31. T u wi h as 33 located at the center of disc 2. no m vemen is imparted t roller :31. ,Howve h fti of t e eas 33 to either side of the center f the disc results in r tation. of r er 3 and s af 3 speed and direction o ota on are dependent upon the posit n of he all ease- Th hall. .caseis carried a the nd o rod :34 connected to the sole oid. pos ti n is hus dependent u on the nos ion of h foll p rm and p oto cells relat ve to he p nd l m A n vel n -b kla h. e system is utilized o rotate h f llow-up a m al.6- his system compr es e members 3. a d 36 ha n arelz e a su fa es -'lihe ear are ea h keyed to he t t na axi of the follow-up arm- G e t mes s w h orn; 3. lseved o shat -2 a d ves to r t h follow-up sys em in one direction. Gear is inter-connected with worm 3.3 a e end of shaft 3?. much e rs 3 '40 and 4!. Gears and 1 are in er-connected f r rotation at h ame rate and ea meshe wi h W r G ar 3 i hel m shin na m with sears A! an .6 b sp in This latter gear arran ement i effect ve to ro e e the follow-up s st m when e direetion f r t of shaft i rever d arran ment eliminates the backlash encountered in i conventional m sear ar an em nts- It will be en that the arr n ement f the p d and ollow-u sy tem s uch that th support a It i otat d su stan i l y in unison with pendulu l5 relat ve o h instrumen case, not shown the drawings, substantially ina a nt on that wou d be otherwise encountered by ei her th friction i the be i t n he pend um susp nsion or h inherent rins ness of the wire the event a torsion uspension of the pen ulum is used.

Obviously the pendulum in this condition would be free to move and would enter into an oscillation in accordance withits period. This oscillation is retarded to considerable extent by the selection of the, particular pendulum of this type which has a long'period. However, it is necessary to further dampen the tendency for oscillation. This maybe. accomplished by .imposing a magnetic flux about the rim of the pen-.- ulumpider 4.3 moun on upport. L6 ee ries the permanent magnets 44 adjacent the pen! dulum rim for this purpose.

Acceleration compensator The pendulum is required to remain in a vertical position under the acceleration force of gravity, however, as the vehicle carrying this apparatus is acceleratedor .decelerated a force due to this movement is imparted to the pendulum at right angles to the earths gravitational force. The resultant force causes the pendulum to deviate from the true. vertical during acceleration or deceleration of the vehicle. One method of compensation has been disclosed in United States Letters Patent 2 ,362,616. The patented compensator depends upon a condenser and for this reason is not entirely satisfactory inasmuch as large high grade condensers are required and in even the best condensers there is a soaking up effect whereby the condenser serves as a galvanic battery and the resultant currents are not proportional to the-vehicle acceleration.

According to this invention thecompensating force is imposed upon or introduced to the pendulum by means of a coupling and .no direct attachments .to the pendulum are employed. Two suitable types of couplings are shown in the drawings. The preferred type is the magnetic type in which the compensating force is introduced to the pendulum by rotating damping magnets in a direction opposite to the forces imposed upon the pendulum by acceleration or deceleration. The resultant movement of the magnetic f ux abnoss the rim of the pendulum imposes a force upon the pendulum equal to and opposite in direction to the force imparted to the pendulum by the vehicle acceleration or deceleration. In this embodiment the force is due to the magnetic flux imposed upon the rim of the pendulum.

In theembodi-ment shown in Fig. 12 the sup.-

port elements 300 replace the magnets and carry a ring member 30]. This ring member serves as an impellerv creating a fluid turbulence between the pendulum and the member due to the air drag created by relative movement of the member and pendulum. Where required a roughened or striated surface may be used on the confronting surfaces of the pendulum and member 301. In some instances the weight of the pendulum may require the use of vanes on the confronting surfaces of member 3.0.! and the pendulum rim. It is to be understood that a fluid coupling employing a, hydraulic liquid can be used in this connection. Referring back to the preferred compensator, a magnet carrier disc 45 carrying permanent magnets 46 is rotatably mounted coaxially with the pendulum. It is then necessary to rotatc the disc proportional to the acceleration and in the proper. direction sense.

The device for deriving the acceleration component of the car s motionconsists of a flat disc 41 carried on the upper end of shaft 48. Spiral ears 49 at theintersecting ends of. shafts 4.8

and 28 provide a connection between the constant speed motor 24 and disc .41. Roller 50 is rotatably mounted above disc 41 and ball cage as mb y 5 simi a to th ssem 3 he tofo e des ibed. se a a o nec i n b tw e the disc and roller to drive the roller in a direction and speed dependent upon the position of the as 5!- The ca is arried and pos t oned y rod 5 The other end f rod 52 o erates w th n a spiral cam gr ove 53a n earn ol er 53- Shaft 54 xtends ax al throu h roller 53 and the right hand end of the, shaft, is inter-connected with roller 50 through a planetary or differential gear assembly. Gear 55 en h esgear 56 which is keyed to the shaft carrying the cage or planetary gear 5] of: the differential system consisting of gears .51, 5 8 and 5.9. Gear 58 is rotationally connected with roller 55%. Gear is attached to gear 59 both of which are rotatably carried upon the shaft to which gear 56 is keyed. Gear 60 in turn is connected to the vehicle wheel 6] through the gear assembly 62, a flexible drive connection 63. and gear as.- sembly 64. The magnetic clutch 55 is interposed in this connection for reasons to be here.- inafter explained in connection with the limit switches.

V The arrangement is such that the planetary gear 51 rotates the crank arm to turngear 5t only when wheel Bl accelerates or decelerates. Thus cam roller 53 is rota-ted only during periods of acceleration or the vehicle. The construction is such-that rod-i2- shifts the ball cage-51 to govern thespe'ed of rotation of roller 50 in proportion to the speed of the car.

A spiral gear assembly 66 serves to rotate disc 45 in proportion to the acceleration or deceleration of the vehicle as therotation of roller 53 is proportional thereto.

Angle corrector and sine converter The above description completes that part of the apparatus relating to the mounting of the pendulum and the compensation for forces that are imposed upon the pendulum other than the true gravitational force. It now remains to correct for the angle deviation of the frame of the apparatus relative to the unsprung vehicle chassis. The corrected angle may then be converted into its sine and integrated over the distance traveled by the vehicle between selected limits. The angle between the pendulum and the case of the apparatus for spring suspended vehicle body is represented by the rotation of roller 3i and shaft 32 which controls the followup system. However, this angular motion does not represent the true angle of the road and must be corrected for the attitude of the spring Of course the unsprung portion of the chassis on the conventional car consists usually of merely the axles and the wheels with no connection with the vehicle body other than through the spring system. A longitudinal reference bar must therefore be provided for connecting the linkage of the parallel arm system from the elevation measuring device. This reference bar must not be subject to strains or distortions by the weaving or twisting of the axles and must maintain a fixed relationship with the contact A surface of the roadway with at least one pair of wheels including one front and one rear wheel.

The preferred manner of accomplishing this is illustrated in Fig. 1. provided with flat surfaces adjacent its ends. The fiat surfaces rest on the radius surfaces 303 of the front and rear axles 304 of the vehicle. The reference bar is held in contact with the radius surfaces of the axles by springs 305 and fastening rods 306. The springs 305 have sufficient tension to hold the reference bar against the surfaces even when traveling over rough roads. The arrangement permits free twisting or weaving of the axles without affecting the linear relationship of bar 68 relative to the contact surfaces of the tires with the roadway or ground surface.

The bar 68 is connected to the parallel arm mechanism including rod 61. Thus, means is provided for correcting for the angular deviation between the spring mounted apparatus frame and the unsprung vehicle chassis.

This difierence is algebraically added to the measured angle represented by rotation of shaft 32 before the sine computer whereby the true angle is continuously and instantaneously fed into the sine computer.

This is accomplished by a differential gear assembly and a parallel arm straight line system A reference bar 68 is of the true angle.

'8 similar to the well known universal drafting machine. The parallel arm system is arranged to transmit angular variations to the crank arm or cage in which the planetary gear is mounted while the rotation of shaft 321s introduced to the input gear of the differential.

The parallel arm system 6'! is attached to the unsprung chassis represented by the rod 68. The arm 61a of the parallel arm system has rigid connection with shaft 69 and the angular motion is introduced into gear 10 keyed to the end of the shaft. Gear 10 meshes with pinion 1| carried by arm 12, the other extremity of which carries a planetary gear 13. The right end of shaft 32 is keyed to input gear 14 of the differential. The angular movement of the output gear 15 of the differential represents the true instantaneous angle between the pendulum and unsprung chassis or rod 68. This angular displacement is transmitted to gear 16 through the pinion gear 11 which is rigidly secured to gear 15. It is to be understood that gears 15 and IT are rotatably mounted on arm 72. The ratio of gears Ti and i6 is adjusted to compensate for the reduction in the angular displacement of shafts 32 and 12 relative to the follow-up system and the parallel arm system whereby the angular displacement of gear 16 is that of the true angle.

The actual sine converter includes the roller 18 mounted on gear 16 and the frame and bar assembly19. The end bar 19a of this assembly abuts roller 18. Suitable means such as springs are provided to hold the bar in contact with the roller. In the interest of simplicity the springs are omitted from the diagrammatic figure but are shown at 238 of Fig. 3 in the embodiment illustrated therein and will be hereinafter more fully described. Rotation of the gear 76 results in a linear reciprocal motion of the assembly 19 proportional to the sine of the angle. This linear motion is introduced into an integrator by means of rod 1% which carries a ball cage in a manner to be hereinafter explained.

Integration mechanism The description of the apparatus has now progressed to the step of integrating the sine of the instantaneous angle times the derivative of the distance traveled by the vehicle between selected limits or in other words, between the points on the earths surface for which the elevation differential is sought. The mechanism for accomplishing this is another adaptation of the rotating disc, balls and roller previously explained in connection with other parts of the apparatus.

The disc 80 is connected to the shaft which carries roller through shaft 8| on which the disc is keyed by the gear assembly 82. It will be recalled that the rotation of roller 50 is proportional to the speed of the car. Therefore, the rotation of disc is also proportional to the vehicle velocity. The ball cage 83 is connected to rod 19?) and is thus positioned relative to the rotating disc 80 and is dependent upon the sine The resultant rotation of roller 84 is then introduced into counter 85 by spiral gear and shaft assembly 86.

The counter is calibrated to the apparatus constant and the difference in the reading at the base or other selected initial point and the reading at any other selected or final point represents the elevation differential between the selected limits.

It is to be understood that in lieu of counter 85 or in addition to the counter 85 the motion T9. of roller 84 may be imposed upon a graph or chart. The preferred means of accomplishing this will be hereinafter more fully explained in coiitiection withFigures 9 to 11 inclusive.

Limit switches Obviously in operation the speed'of the vehicle as well as the angle 'of the unsprung chassis relative to the horizontal should be maintained within certain limits depending upon the characteristics or setting of the apparatus. The limit switches to be described provide a protective system which disconnects the drive and lights a signal lamp or energizes any other suitable. alarm when either the speed limit is exceeded or when too steep an angle is encountered. In such cases the operator must go back to the last station of known elevation and re-survey after making the requisite adjustments of the apparatus.

The means of accomplishing this comprises the magnetic clutch 65, an electrical circuit including an alarm 81. limit switches 88 responsive tolug 19c carried by the sine converter frame 19 and limit switch 89 responsive to the upturned portion of rod 52 of the acceleration compensator. A single source of electrical energy 80 may be utilized to energize the constant speed motor 24; the magnetic clutch B and the limit switches 88 and 89. In operation the limit switches are normally open and switch 9| is normally closed. A relay '9; makes electrical connection with that part of the circuit energizing the magnetic clutch. The arrangement is such that when either of the limit switches 88 or 89 are closed the relay is energized breaking the connection to the magnetic clutch and making connection with the alarm 81.

C'har ting mechanism As indicated earlier in the descriptioni the apparatus may utilize in place of the counter 85 a recording device which will draw a profile of the path traversed by the vehicle. However, it is usually preferable to utilize both the recording device and counter. p

In most areas, substantial elevation differentials are encountered and in order to have a chart with a large scale the novel system of recording illustrated in Figs. 9 to 11 inclusive is required.

system is based upon a recording apparatus' that will plot a predetermined variation of altitude about the center line of the chart as indicated in Fig. 11. When the chaff, limit is reached by the marking element then the marker is automatically returned to the center of the v record where it continues to plot the elevation variations. A convenient make up for the chart is shown, that is, the distance from the center line to the edges of the chart represents variatier;- of ten feet in altitude. With; this roller 93', the-shaft ofwhich is rotatably interconnected with wheel e l of th'e" vehicle through gear 9'4 which meshes with one 6i; thelgeair's" of the assembly 52-" as indicated in Fig. r. Thus; the chart is rotated accordingto the speed of" the vfiibl'. The mechanism 1'61 dOfitidllifi the marker :94 includes the pulley wheels 95 and 96. Wheel 95 rotatablyeonhected some *shait on which roller 184 is inounte'd; Around the pulleys is "an endless belt or chin 9"! having wedge shaped protrusions or carriers 91a. The spaces between the apexes of the wedges are exactly the same as the cistance ir'o'm the center of the chart to either edge. Support arms 98 carry guide rods 99 and 00. on each or the rods are slidablymounted'bushings I01 and I02. Mounted between the bushings is the marker carrier 193 On which marker 9 4 'is mounted. Extending from and pivoted to the end of the carrier is a latch 10!. The latch has a web shaped recess for receivingthe wedge Md. The latch has beveled edges 1 4d'at'eacli side. When the chain or be1t'91 carries the latch and bushing inechanismt?) either side to the point that the marker reaches the edge or the chart the tapered ends of arms H15 engage the tapered surfaces ltdaof the lateh, lifting'tne latch from the particular wedge 91;; upenwhich it has been positioned. When thus 'fele'aseutne springs I06. attached between the bushings and su ports 98 return the bushings -a'n'd latch assembly to the center position where another wedge 91a is engage'd by the latch-recess. v p

It is believed that the operation of this than: ing mechanism is apparent from the foregoing description. The pulley wheel 95 is rotated by the integral roller 84 in roportion to the 'ele'- vati'on variation. The maiker carrier I03 due to the connection between latch I04 and belt 9'! is moved along a line normal to the chart axis as it passes over roller 93. The roller is advanced past the marker in proportion to the speed of the vehicle. When a variation in either direction is encountered greater than the distance represented by one half /2) the chart width, the marker makes a rapid excursion, back to the center line" of the'chart and recording is con tinned to produce the saw to'oth type chart illustrated in Fig. 11.

It is contemplated that servomoto'rs may be employed in place of all or either of the power devices shown in the former the rotating disc, roller and ball cage assemblies, as will be understood by thoseskilled in the art. However; the assemblies shown are preferred as they substantially eliminate the necessity of intricate electrical arrangements.

The preferredmadam-em The preferred embodiment illustrated in Figs. 2 to 8 inclusive of the drawingswill now be considered. The base platform 20!) serves as a support for the device on which the mechanism described in conjunction with Fig. 1 is mounted. Upright pedestal 2Q]; has at its upper enda bearing ir'iwhich the shait for follow-up arm; l5 is journaled Photoelectric 11 carrier I9 is mounted a he fdllowup afrn adjacentits shaft and housed within the carrier are photoelectric dens" IT [ii away portions of th has i an inverted u shaft of the pendulu pm- 295-. This pin is threaded the lion-6w The pendiimm s has Disc 45 which carries the magnets 45 of the acceleration compensator has a central shaft 45a. The shaft has a ball bearing mounting in the upper end of pedestal 206. The spiral gear assembly 66 and the drive assembly therefore will be hereinafter discussed.

Disc 45 carries a cylindrical portion 451). This cylindrical portion carries the magnets 45 and in conjunction with the disc serves as a light box supplying light to photo cells through the upper cut-away portion of pendulum 15. The lamp 213 which supplies the light to the box through the lower cut-away portion of the pendulum is supported from arm 16 by bracket 201. The magnets 44 are connected through braces 43 to the rods 203a.

The gears for rotating the follow-up shaft and system are illustrated in Figs. 2, and 6. Gears and 315 are rigidly connected to the follow up shaft. The lower portion of these gears opcrate within case 208. Shaft 32 is journaled in the ends of the case. Gears 43 and 41 are mounted on the shaft 209 which is in turn journaled in case 203. Gear 39 is rotatably carried by an assembly 210 mounted by means of spring 42 to the case. The amplifier 22 is mounted on platform 293 and is connected by cables 211 and 212 to the electric eyes 1'1 and i8, respectively.

An upright boxlike partition 213 provides a F support for the servomotor or solenoid 23. The active ends of the solenoid extend on either side of the boxlike partition. The rod of the solenoid passes through openings in the walls of the partition. The ball cage 33 has ears 33a having a slidable connection upon rod 214, the ends of which are secured to the walls of partition 213. This sliding connection on the rod supports both the ball cage and solenoid. An arm 33?) extends from ball cage 33 and is attached to the ends of and gear 27 meshing therewith are mounted within partition 213. Drive shaft 28 and the spiral gears 30 and 49 are combined to drive shaft 48 and the shaft 211. These shafts are journaled in brackets 218 which are removably secured to bracket 216 and the partition 213. Meshing gears 219 and 229 serve to transmit the driving power to disc 29.

To simplify the description it may be said at this point that disc 4'1, which comprises a part of the disc, ball and roller assembly 4'1, 51 and of the accelerated compensation device is similarly mounted in the boxlike partition 2E3 as illustrated. Similar gears, shafts and brackets are designated by like numerals. A guide pin 221' extends in each instance from brackets 218 into a horizontal groove in ball cages 33 and 51 for added support.

Shaft 32 on which roller 31 is mounted is journaled in the walls of partition 213 and at one end is journaled in and extends through the walls of another upright boxlike partition 222. Gear 74 of the differential is driven from shaft 32 by means of pinion gear 223. The planetary gears of this differential are attached to the cage 224 Somewhat different gear arrangeof the differential and are not visible in the drawing. Gear 15 of the difierential meshes with an intermediate gear 225 keyed to the same shaft as is spiral gear '11, which in turn meshes with gear '10. Shaft 69 to which gear 10 is keyed extends through the partition 226 intermediate box like partitions 213 and 222. This shaft has an operable connection through parallel arm and straight line mechanism 61, not shown in the drawings, to the unsprung vehicle chassis. In this embodiment the gear '11 is connected to the output gear '15 of the differential through gears 221, 228, shafts 229 and 230. These shafts, as well as shaft '12, are journaled in the walls of partition 22.

The description has now progressed to the mechanism for driving the acceleration compensator and more particularly to the disc roller and ball cage assembly and related parts designated by numerals 41, 50 and 51, respectively, the mounting of which has been heretofore explained. It will be seen that shaft 54 carrying cam roller 53 is journaled in the walls of partition 213 in such fashion that the cam slot 53a of the roller engages the lug or rod 52 attached to ball cage 51.

Roller 50 is connected to the vehicle wheel, not shown in the drawings, by spiral gear assembly 64 detailed in Fig. 8. These gears and the shafts on which they are mounted, as well as the magnetic clutch 65, are mounted within box 231 which in turn is mounted on platform 2311.

In this embodiment the differential gear connection between roller 51, the magnetic clutch and cam roller 53 is reversed compared to the illustration of Fig. 1. In other words, gear 69 driven by the magnetic clutch meshes with the input gear 58 of the differential. While the shaft on which roller 50 is mounted is connected to the difi'erential cage, the output gear 59 meshes with gear to drive the cam roller 53. The connection between the spiral gear assembly 66 for driving the acceleration compensator disc 45 is connected to the cam roller through shaft 232, and gears 233 and 234. Shaft 232 is mounted for rotation between the wall of partition 213 and bracket 293a. carried by pedestal 206.

The shaft on which roller 56 is mounted extends through the differential whose input and output gears are designated as 58 and 59, respectively. The gear assembly 82 of Fig. 1 is replaced by gear 235 keyed to the roller shaft. Gear 235 meshes with gear 235 mounted thereabove. Shaft 81 on which gear 236 is rigidly mounted is journaled in frame 231 which frame is attached by a 1 suitable bracket 238 to partition 239, extending vertically from platform 209. Frame 23'! also serves as a mounting for the disc, ball and roller assembly designated by numerals 30, 83 and 84, respectively.

Frame 23! slidably supports the sine computer frame '19 as shown in Fig. 3. The rod 191) of the frame is connected to the ears 83a of the ball cage to control its position relative to disc 85. Springs 238 urge roller bar 79a into engagement with roller 18.

Counter is mounted on frame 237. The gear drive between the counter and output shaft of roller 84 is supported by cage 239 attached to frame 231 by bracket 240.

From the foregoing it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth together with other advantages which are obvious and which are inherent to the structure.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is Within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

Having described my invention, I claim:

1. In a device for determining diiferences in elevation between separate points on the earths surface a pendulum in the form of an unsymmetrical disc operably mounted to provide a vertical reference co-ordinate, an acceleration compensator including a magnet carrier rotatably mounted in axial alignment with the pendulum, magnets connected to the carrier in such manner as to impose a magnetic flux about the pendulum rim and means to rotate the carrier solely in response to acceleration and deceleration of the device, the directional sense of rotation in each instance being opposite to that which would be imparted to the pendulum by such acceleration change, the arrangement of the magnets and the means to rotate the carrier being such as to provide a torque acting on the pendulum equal and opposite to that due to acceleration or deceleration of the instrument.

2. In a device for determining differences in elevation between separate points on the earths surface, a pendulum in the form of an unsymmetrical disc operably mounted to provide a vertical reference co-ordinate, an acceleration compensator including a rotatable member mounted coaxially with the axis of movement of said pendulum, means to drive and rotate the member solely in response to the acceleration of the device and in a directional sense opposite to that which would be imparted to the pendulum by such acceleration, magnets carried by the member in close proximity of the peripheral rim of the pendulum disc so as to impose a magnetic flux about the rim of the pendulum, the arrangement of the magnets and the means to rotate the member being such as to provide a torque acting on the pendulum equal and opposite to the torque acting thereon due to acceleration or deceleration of the instrument.

3. In a device for determining differences in elevation between separate points on the earths surface, a pendulum in the form of an unsymmetrical disc operably mounted to provide a vertical reference co-ordinate, an acceleration compensator including a rotatably mounted member, magnets carried by the member and disposed about and closely adjacent the peripheral rim of the pendulum disc, and linkage including a differential gear system having its output gear connected with the member to rotate the member and its input gears connected respectively with a wheel upon a vehicle upon which the device may be mounted and a gear adapted to rotate at a rate responsive to the instantaneous speed of the vehicle, the linkage and mounting of the member being such that rotation of the output gear will rotate the member in a directional sense opposite to the torque on the pendulum due to acceleration, the arrangements of the magnets and the linkage for rotating the member carrying the magnets being such as to provide a torque acting on the pendulum equal and opposite to the torque acting thereon due to acceleration and deceleration of the instrument.

4. In a device for determining differences in elevation between separate points on the earths surface, a pendulum in the form of an unsymmetrical disc operably mounted to provide a reference co-ordinate, an acceleration compensator including a member rotatably mounted coaxially with the axis of movement of said disc, magnets carried by the member and disposed about and closely adjacent the peripheral rim of said disc and means to rotate said member in response to acceleration of the device and in a rotative direction opposite to that which the acceleration tends to urge said disc including a differential gear system having its output gear connected with said member to rotate the same and having a first input gear connected with a wheel of a vehicle upon which the device may be mounted and a. second input gear connected with means for driving the same at a rate proportional to the speed of the vehicle including a connection between the output gear and the driving means for changing the rate at which the second input gear is driven by said means proportionally to a change in rate of rotation of said first input gear, the arrangement of the magnets and the means for rotating said member being so proportioned as to provide a torque acting on said disc equal and opposite to the torque acting thereon due to acceleration and deceleration of a vehicle which may carry the device.

RAYMOND T. CLOUD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 95,758 Barton Oct. 12, 1869 624,268 Uehling May 2, 1899 681,835 Soldona Sept. 3, 1901 1,100,698 Stoddard June 16, 1914 1,542,809 Alexander et al. June 23, 1925 1,567,347 Van Lynden Dec. 29, 1925 1,571,820 Turner Feb. 2, 1926 2,176,807 Wunsch Oct. 17, 1938 2,224,954 Eisle Dec. 17,1940 2,320,290 McNatt May 25, 1948 2,362,616 Cloud Nov. 14, 1944 2,381,225 Newell Aug. 7, 1945 2,429,620 Harrington Oct. 28, 1947 FOREIGN PATENTS Number Country Date 230,186 Great Britain 1925 404,303 Great Britain 1934 530,764 Germany 1931 

